Yahoo Groups archive

Lpc2000

Index last updated: 2026-04-28 23:31 UTC

Thread

MAX232 and P1.20/P1.26 pins.

MAX232 and P1.20/P1.26 pins.

2005-06-19 by Boris Estudiez

19/06/2005 - 01:25 AM

Hello,

#1)

Can I use a MAX232 (+5V Logic) with a LPC21xx (+3.3V Logic) ?.
Have you used it?, It works fine?. 

Note: I can't find a MAX3232 (+3.3V logic) in my country.

#2)

From LPC21xx Philips datasheet:

"P1.20: LOW in this pin while /RESET is LOW, enables pins P1.25:16
to operate as Trace port after reset."
"P1.26: LOW in this pin while /RESET is LOW, enables pins P1.31:26
to operate as Debug port after reset."

I don't want to use Trace and Debug port. 
Should I connect P1.20 and P1.26 pins to +3.3V (via pull-up resistors) ?.
It's necessary ?. Can I leave unconnected that pins ?.

Thanks in advance.

Boris Estudiez.-

-- 

Contacteme en:
* Mail(1): stk@...
* Mail(2): 43824@...
* Mail(3): slicetex@...
* Website: http://stk.freeshell.org
EOF

Re: [lpc2000] MAX232 and P1.20/P1.26 pins.

2005-06-19 by Leon Heller

----- Original Message ----- 
Show quoted textHide quoted text
From: "Boris Estudiez" <boris_tormentor@...>
To: <lpc2000@yahoogroups.com>
Sent: Sunday, June 19, 2005 5:31 AM
Subject: [lpc2000] MAX232 and P1.20/P1.26 pins.


> 19/06/2005 - 01:25 AM
> 
> Hello,
> 
> #1)
> 
> Can I use a MAX232 (+5V Logic) with a LPC21xx (+3.3V Logic) ?.
> Have you used it?, It works fine?. 
> 
> Note: I can't find a MAX3232 (+3.3V logic) in my country.


I've tried it and it works OK.

Leon


-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.323 / Virus Database: 267.7.8/22 - Release Date: 17/06/2005

---
[This E-mail has been scanned for viruses but it is your responsibility 
to maintain up to date anti virus software on the device that you are
currently using to read this email. ]

Re: [lpc2000] MAX232 and P1.20/P1.26 pins.

2005-06-19 by Anton Erasmus

On 19 Jun 2005 at 1:31, Boris Estudiez wrote:

> 19/06/2005 - 01:25 AM
> 
> Hello,
> 
> #1)
> 
> Can I use a MAX232 (+5V Logic) with a LPC21xx (+3.3V Logic) ?.
> Have you used it?, It works fine?. 
> 
> Note: I can't find a MAX3232 (+3.3V logic) in my country.
> 
[Snipped]

There quite a number of other companies that make 3.3V RS-232 buffers.
I often use the Analog Devices products since they are available in small quantities
and are always at least industrial spec. ADM3202 or ADM3222. These devices are 
specced for both 5V and 3.3V so one can use the same device for a 5V or 3.3V design.

Regards
   Anton Erasmus-- 
A J Erasmus

Re: [lpc2000] MAX232 and P1.20/P1.26 pins.

2005-06-19 by Robert Adsett

At 11:07 AM 6/19/05 +0200, Anton Erasmus wrote:
>On 19 Jun 2005 at 1:31, Boris Estudiez wrote:
>
> > 19/06/2005 - 01:25 AM
> >
> > Hello,
> >
> > #1)
> >
> > Can I use a MAX232 (+5V Logic) with a LPC21xx (+3.3V Logic) ?.
> > Have you used it?, It works fine?.
> >
> > Note: I can't find a MAX3232 (+3.3V logic) in my country.
> >
>[Snipped]
>
>There quite a number of other companies that make 3.3V RS-232 buffers.
>I often use the Analog Devices products since they are available in small 
>quantities
>and are always at least industrial spec. ADM3202 or ADM3222. These devices 
>are
>specced for both 5V and 3.3V so one can use the same device for a 5V or 
>3.3V design.

TI also produces 3.3V versions I use their MAX3238.  Mouser also crosses 
the max3232 to an ST part so they may be worth checking as well.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/

Re: [lpc2000] MAX232 and P1.20/P1.26 pins.

2005-06-19 by Robert Adsett

At 01:31 AM 6/19/05 -0300, Boris Estudiez wrote:
> From LPC21xx Philips datasheet:
>
>"P1.20: LOW in this pin while /RESET is LOW, enables pins P1.25:16
>to operate as Trace port after reset."
>"P1.26: LOW in this pin while /RESET is LOW, enables pins P1.31:26
>to operate as Debug port after reset."
>
>I don't want to use Trace and Debug port.
>Should I connect P1.20 and P1.26 pins to +3.3V (via pull-up resistors) ?.

Yes.

>It's necessary ?

I think so.  At the very least it's good defensive practice and gives you 
pads to connect to if you want to probe  or add to the area.

Speaking of datasheets.  Is anyone else having trouble getting them from 
Philips site?  I keep getting "the page you requested is not 
available".  This is the link I end up following

http://www.semiconductors.philips.com/acrobat_download/datasheets/LPC2104_2105_2106-05.pdf

Of course Philips site is probably one of the slowest on the web, I 
actually timed the 2104 product page and it took 1/2 a minute to render, 
and that discourages a lot of exploration.

Hmm, I just checked with IE.  It seems to be specific to firefox.  Render 
speed is about the same for both, turning javascript off (I usually do but 
for some reason it was on) helps a lot.  I'll try a few other systems to 
see if I can nail down what is happening with the pdf download.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/

Re: [lpc2000] MAX232 and P1.20/P1.26 pins.

2005-06-19 by Leon Heller

----- Original Message ----- 
Show quoted textHide quoted text
From: "Robert Adsett" <subscriptions@...>
To: <lpc2000@yahoogroups.com>
Sent: Sunday, June 19, 2005 6:01 PM
Subject: Re: [lpc2000] MAX232 and P1.20/P1.26 pins.


> At 01:31 AM 6/19/05 -0300, Boris Estudiez wrote:
>> From LPC21xx Philips datasheet:
>>
>>"P1.20: LOW in this pin while /RESET is LOW, enables pins P1.25:16
>>to operate as Trace port after reset."
>>"P1.26: LOW in this pin while /RESET is LOW, enables pins P1.31:26
>>to operate as Debug port after reset."
>>
>>I don't want to use Trace and Debug port.
>>Should I connect P1.20 and P1.26 pins to +3.3V (via pull-up resistors) ?.
>
> Yes.
>
>>It's necessary ?
>
> I think so.  At the very least it's good defensive practice and gives you
> pads to connect to if you want to probe  or add to the area.
>
> Speaking of datasheets.  Is anyone else having trouble getting them from
> Philips site?  I keep getting "the page you requested is not
> available".  This is the link I end up following
>
> http://www.semiconductors.philips.com/acrobat_download/datasheets/LPC2104_2105_2106-05.pdf
>
> Of course Philips site is probably one of the slowest on the web, I
> actually timed the 2104 product page and it took 1/2 a minute to render,
> and that discourages a lot of exploration.
>
> Hmm, I just checked with IE.  It seems to be specific to firefox.  Render
> speed is about the same for both, turning javascript off (I usually do but
> for some reason it was on) helps a lot.  I'll try a few other systems to
> see if I can nail down what is happening with the pdf download.

I just accessed the LPC2106 page with IE and it took under 2s! I have a 4 Mb 
broadband connection (soon to be updated to 8 Mb) which helps.

Leon 


---
[This E-mail has been scanned for viruses but it is your responsibility 
to maintain up to date anti virus software on the device that you are
currently using to read this email. ]

Re: [lpc2000] MAX232 and P1.20/P1.26 pins.

2005-06-19 by Leonardo

You can use a MAX232 of Texas Instruments (easy to find), because the Vih of this is 2V (min), then you can connect 3V3 pin of uC directly (as TX), in another direction (RX), you can use a simple voltage divider, with resistors to do the 3V3 signal to uC. The disadvantage of MAX232 is capacitors are bigger than in a MAX3232 device (100nF typical). The most important parameter is Vih (min) than be smaller than I/O port voltage.  

Leo
Show quoted textHide quoted text
  ----- Original Message ----- 
  From: Leon Heller 
  To: lpc2000@yahoogroups.com 
  Sent: Sunday, June 19, 2005 2:16 PM
  Subject: Re: [lpc2000] MAX232 and P1.20/P1.26 pins.


  ----- Original Message ----- 
  From: "Robert Adsett" <subscriptions@...>
  To: <lpc2000@yahoogroups.com>
  Sent: Sunday, June 19, 2005 6:01 PM
  Subject: Re: [lpc2000] MAX232 and P1.20/P1.26 pins.


  > At 01:31 AM 6/19/05 -0300, Boris Estudiez wrote:
  >> From LPC21xx Philips datasheet:
  >>
  >>"P1.20: LOW in this pin while /RESET is LOW, enables pins P1.25:16
  >>to operate as Trace port after reset."
  >>"P1.26: LOW in this pin while /RESET is LOW, enables pins P1.31:26
  >>to operate as Debug port after reset."
  >>
  >>I don't want to use Trace and Debug port.
  >>Should I connect P1.20 and P1.26 pins to +3.3V (via pull-up resistors) ?.
  >
  > Yes.
  >
  >>It's necessary ?
  >
  > I think so.  At the very least it's good defensive practice and gives you
  > pads to connect to if you want to probe  or add to the area.
  >
  > Speaking of datasheets.  Is anyone else having trouble getting them from
  > Philips site?  I keep getting "the page you requested is not
  > available".  This is the link I end up following
  >
  > http://www.semiconductors.philips.com/acrobat_download/datasheets/LPC2104_2105_2106-05.pdf
  >
  > Of course Philips site is probably one of the slowest on the web, I
  > actually timed the 2104 product page and it took 1/2 a minute to render,
  > and that discourages a lot of exploration.
  >
  > Hmm, I just checked with IE.  It seems to be specific to firefox.  Render
  > speed is about the same for both, turning javascript off (I usually do but
  > for some reason it was on) helps a lot.  I'll try a few other systems to
  > see if I can nail down what is happening with the pdf download.

  I just accessed the LPC2106 page with IE and it took under 2s! I have a 4 Mb 
  broadband connection (soon to be updated to 8 Mb) which helps.

  Leon 


  ---
  [This E-mail has been scanned for viruses but it is your responsibility 
  to maintain up to date anti virus software on the device that you are
  currently using to read this email. ]



------------------------------------------------------------------------------
  Yahoo! Groups Links

    a.. To visit your group on the web, go to:
    http://groups.yahoo.com/group/lpc2000/
      
    b.. To unsubscribe from this group, send an email to:
    lpc2000-unsubscribe@yahoogroups.com
      
    c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. 



[Non-text portions of this message have been removed]

Re: [lpc2000] MAX232 and P1.20/P1.26 pins.

2005-06-19 by Robert Adsett

At 06:16 PM 6/19/05 +0100, Leon Heller wrote:
>----- Original Message -----
>From: "Robert Adsett" <subscriptions@...>
> > Speaking of datasheets.  Is anyone else having trouble getting them from
> > Philips site?  I keep getting "the page you requested is not
> > available".  This is the link I end up following
> >
> > 
> http://www.semiconductors.philips.com/acrobat_download/datasheets/LPC2104_2105_2106-05.pdf
> >
> > Of course Philips site is probably one of the slowest on the web, I
> > actually timed the 2104 product page and it took 1/2 a minute to render,
> > and that discourages a lot of exploration.
> >
> > Hmm, I just checked with IE.  It seems to be specific to firefox.  Render
> > speed is about the same for both, turning javascript off (I usually do but
> > for some reason it was on) helps a lot.  I'll try a few other systems to
> > see if I can nail down what is happening with the pdf download.
>
>I just accessed the LPC2106 page with IE and it took under 2s! I have a 4 Mb
>broadband connection (soon to be updated to 8 Mb) which helps.

The problem doesn't appear to be transfer time, but rather render 
time.  The link for data transfer only takes a couple of seconds, the rest 
of the time is spent figuring out how to display it.  One of the processors 
pegs to 100% during this.  Since turn off javascript cuts the time to 10% 
to 20% of the time with javascript on it looks like they are doing a lot of 
unnecessary fooling around with the display.  I expect you are using a 
faster processor for browsing then I am. Unfortunately Philips appears to 
have one of the sites that cripples itself when javascript is turned off, 
for no good reason that I can see.

The pdf download is, I think, an unrelated issue that I will try to track 
down as I get some time.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/

Re: [lpc2000] MAX232 and P1.20/P1.26 pins.

2005-06-20 by Alex Holden

On 19 Jun 2005, at 19:20, Robert Adsett wrote:
> The problem doesn't appear to be transfer time, but rather render
> time.  The link for data transfer only takes a couple of seconds,  
> the rest
> of the time is spent figuring out how to display it.  One of the  
> processors
> pegs to 100% during this.  Since turn off javascript cuts the time  
> to 10%
> to 20% of the time with javascript on it looks like they are doing  
> a lot of
> unnecessary fooling around with the display.  I expect you are using a
> faster processor for browsing then I am. Unfortunately Philips  
> appears to
> have one of the sites that cripples itself when javascript is  
> turned off,
> for no good reason that I can see.

I have the same problem with Safari on an 800Mhz G4. The Philips  
product pages are painful to navigate because the pages each take  
about a minute of 100% CPU time to render (really). Safari 2.0 is  
supposed to have a much faster Javascript engine than Safari 1.0 but  
I haven't noticed a significant improvement with the Philips pages. I  
haven't seen this problem with any other site on the web.

-- 
------------ Alex Holden - http://www.alexholden.net/ ------------
If it doesn't work, you're not hitting it with a big enough hammer

Move to quarantaine

This moves the raw source file on disk only. The archive index is not changed automatically, so you still need to run a manual refresh afterward.